The present invention relates to a travelling vehicle equipped with obstacle detector sensors. 2. Description of the Prior Art
A conventional travelling vehicle equipped with obstacle detector sensors, for example a mowing machine vehicle of the automatic travelling type, generally requires means for sensing an obstacle potentially located forward with respect to the travelling vehicle to stop the vehicle body, thereby to avert danger or collision. Such means inevitably need sensors capable of accurately and reliably sensing the presence of an obstacle. Noncontact-type sensors, such as photo-sensors or ultrasonic sensors, and contact-type sensors for mechanically sensing an obstacle with the use of bumpers or feeler bars are known. Such conventional sensors, however, present inconveniences as will be described below.
In the noncontact-type sensors, design considerations are made not only to provide a long and safe braking distance between the obstacle detection and vehicle travelling stop positions, but also to allow a certain latitude in the obstacle detectable range. Accordingly, there arises the possibility of an obstacle being detected to stop the vehicle travelling at an unnecessarily remote position, thereby lowering the working efficiency of the vehicle.
On the other hand, a contact-type sensor is structurally designed so as to sense an obstacle by mechanically contacting the obstacle. Therefore, when the sensor comes into contact with an obstacle with the vehicle travelling at a high speed, the vehicle cannot be immediately stopped thereby causing potential danger. Moreover, conventional contact-type sensors require a complicated structure so as to safely absorb the mechanical shock when the vehicle comes into contact with an obstacle.